1. Field of the Invention
The instant disclosure relates to a multi-phase boost converter with phase self-detection and a detecting circuit thereof; in particular, to a multi-phase boost converter with phase self-detection and a detecting circuit thereof which can determine whether to control the switching transistors of each phase by detecting if an inductor of each phase of the multi-phase boost converter exists, so as to decrease unnecessary power consumption.
2. Description of Related Art
An electronic device usually contains various different elements, and the operation voltage of each element may also be different. Thus, in the electronic device, a DC to DC voltage converter is needed to achieve the regulation of the voltage level (rising the voltage or decreasing the voltage), such that each element can receive a stable voltage level. Depending on different power requirements, a variety of DC/DC voltage converters are proposed. However, all proposed voltage converters come from improvement of the buck/step down converter and the boost/step up converter. The buck converter decreases the DC voltage of the input end to a preset voltage level, and the boost converter increases the DC voltage of the input end.
Please refer to FIG. 1, FIG. 1 shows a circuit diagram of a conventional single-phase boost converter. A single-phase boost converter 1 comprises an inductor L1, a first switch LG1, a second switch UG1, a capacitor 11, a feedback circuit 13 (which can be a voltage dividing circuit composed of some resistors), and a pulse width modulation (PWM) controller 15. The PWM controller 15 obtains a feedback voltage generated based on the output voltage VOUT from a feedback node 101 of a feedback circuit 13, and the PWM controller 15 controls the conduction/cut-off status of the first switch LG1 and the second switch UG1 according to the feedback voltage, for adjusting the voltage level of the output voltage VOUT.
For example, when the single-phase boost converter 1 finds out that the output voltage VOUT is less than a specific voltage level, the single-phase boost converter 1 will enter the boost mode. At the same time, the second switch UG1 will be cut-off, and the first switch LG1 will be conducted, such that the input voltage Vin will charge the inductor L1. Then, the second switch UG1 will be conducted, the first switch LG1 will be turned off, and the inductor L1 will charge the capacitor 11, such that the output voltage VOUT will rise to another specific voltage (which is greater than the voltage level of the input voltage Vin).
Then, please refer to FIG. 2 showing a circuit diagram of a conventional multi-phase boost converter. A multi-phase boost converter 2 comprises inductors L1˜Ln, first switch LG1˜LGn, second switch UG1˜UGn, a capacitor 11, a feedback circuit 13 and a PWM controller 15. The multi-phase boost converter 2 shown in FIG. 2 can be considered as n of the single-phase boost converters 1 shown in FIG. 1 connected in parallel in equivalence. Therefore, the input current of the multiphase boost converter 2 is actually the summation of the currents of the n inductors L1˜Ln. And, the current ripples of the n inductors L1˜Ln may be out of phase to a certain degree, such that the ripple of currents of the n inductors L1˜Ln may be cancelled by each other. In other words, for the conventional boost converter, by increasing the number the phases of the boost converters, the effect of decreasing the input current ripple and the output voltage ripple caused by the inductors can be achieved, and this favors high power applications.
In summary, multi-phase boost converter has higher reliability and efficiency compared to the single-phase boost converter, such that the multi-phase boost converter has become one of the mainstream applications. However, in a low power operation environment, there is no need to apply a large input current. Therefore the user may apply a certain manner to cease the operation of some phases where the inductors are disconnected, thus the related operation quiescent current of circuitry and the corresponding switching loss can be saved. Referring to FIG. 2 as an example, the amount of the inductors L1˜Ln can be removed in order to reduce component costs in low power operation environment. However, the phase without inductor still switches, therefore, the related operation quiescent current of circuitry is then wasted and of course the corresponding switching loss is not saved. If one or some inductor are intentionally removed, the conventional multi-phase boost converter 2 does not provide any internal control mechanism for detecting its inductors L1˜Ln, for determining whether any or some of the inductors L1˜Ln have been removed (for example, the inductor is opened). Thus, the PWM controller 15 still controls the first switch LG1˜LGn and the second switch UG1˜UGn, so as to result in unnecessary power consumption.